urban areas aren't all white collar, there are plenty of other jobs around.

But thats just part of the problem. Why would a company want to build an office building in the middle of an ocean at the huge premium....when they can just build one on land? I mean if a company wants to put its offices in the middle of nowhere there are plenty of cheaper alternatives.

You have to remember, that the cost of living on something like this would be huge, since they'll need to import all their food, and living space would be at a premium.